Polar Biol (1986)6:127-137 ^^ O ojioio © Springer-Verlag 1986

Polymorphism and Distribution of trilobitoides (Eights, 1833) (Crustacea, ) in the Weddell Sea and Synonymy with C cornuta (Studer, 1879)

Johann-Wolfgang Wagele

Arbeitsgruppe Zoomorphologie, Fachbereich Biologie, Universitat Oldenburg, D-2900 Oldenburg, Federal Republic of Germany

Received 26 June 1985; accepted 3 April 1986

Summary. A rich collection of Ceratoserolis trilobitoides Bremerhaven in a temperature-controlled container. To study pigmen­ from the Antarctic Peninsula and the western and south­ tation and behaviour living specimens were photographed on board. Drawings were prepared with a stereomicroscope "Wild M5" and a ern Weddell Sea is evaluated to describe the poly­ camera lucida. morphism and variations of the pigmentation. The spe­ Several hundred specimens of C. trilobitoides were caught, in 43% cies is very variable, though local populations show a of all samples (between 20 and 1,145 m depth) this species was present relatively homogenous morphology. Transitional forms (for distribution see Fig. 1). The sampling method allows no further connect different morphotypes. Presumably the relative quantitative analysis. For comparison of morphological variations populations from the immobility of these , together with low fecundity following stations were studied: and geographical or hydrographical barriers are respon­ 62°38.81'S 55°45.20'W, depth 277 m (north of Joinville Island, Brans- sible for the evolution of local races. C cornuta and the field Strait), 62°8.84'S 58°0.46'W, depth 449 m (entrance of Admira- "colour-species" of Cals (1977) are synonymized with C. lity Bay, King George Island), 60°42.40'S 45°33.07'W, depth 86 m (off Signy Island), 72°30.35'S 17°29.88'W, depth 240-254m (Vestkapp), trilobitoides. 74°39.25'S 25''18.86'W, depth 605-610 m (northeast of Halley Bay), 77°42.25'S 36°48.09'W, depth 1,145 m (Filchner-depression), 77°31.67'S 42°12.42'W, depth 592- 630 m (Gould Bay). Introduction For comparison the following material, previously described by Studer (1879, "Gazelle"-collection) and Sheppard (1933, "Discovery"- During the expeditions 1982/83 and 1984/85 oi RV collection) was used: Polarstern among the soft-bottom benthic of " cornuta": specimens from Kerguelen, 47°52'S 66°41'E, the Weddell Sea the conspicuous seroUd isopods could be "Gazelle"-collection (Zoologisches Museum Berlin, Kat. Nr. 4601); k collected in large numbers. These are carnivorous ani- "Discovery" station 363 (B.M.N.H. 1934. 10. 16.: 809-810) and "Discovery" station 164 (B.M.N.H. 1934. 10. 16.: 811-814). mals which Uve, often half buried, on the sandy or mud­ "Serolis trilobitoides": "Discovery station 170 (B. M. N. H. 1934. dy sea-floor. The biggest species, Ceratoserolis trilo­ 10. 16.: 845-846), "Discovery" station 172 (B.M.N.H. 1934. 10. 16.: bitoides, a disc-shaped , has an obvious variation 847-850). of colour pattern, which has been described already by Cals (1976, 1977), who erected four new species on the base of pigments and cuticular scales. To estimate the validity of these species a study of polymorphism based Results on a large number of specimens became necessary. In the present study the morphotypes of populations from the A) Distribution Weddell Sea and the Antarctic Peninsula are described and causes for the variations and the systematic con­ Figure 1 shows the new localities. C, trilobitoides has sequences are discussed. previously been found at the Antarctic Peninsula, the South Shetlands and South Orkneys, but not in the Wed­ dell Sea. Figure 2 shows the places from which the Material and Methods species is known so far. It colonizes an enormous area, from the subantarctic Crozet-Islands (Studer 1879) to the Samples of benthos were collected from R V Polarstern during the sea floor under the Ross Ice Shelf (Lipps et al. 1979); it expeditions 1982/83 and 1984/85 by means of an Agassiztrawl. In­ has a circumpolar distribution. The Patagonian localities vertebrates were sorted out on deck by hand, sediment was washed through a 1 mm-sieve. During the last expedition living specimens were (Eights 1833) are dubious, possibly other serolids were immediately placed in aquaria, wherein they were transported to taken for C. trilobitoides. New discoveries from this area 128

60 S 60S

70 S -70 S

Fig. 1. The new localities where C. trilobitoides was found (Antarctic Peninsula and Weddell Sea)

are not known, though some authors have foUowd the earlier statements (e.g. Nordenstam 1933). C. trilobitoides is obviously a species which prefers soft bottom and therefore is not present on some shallow littoral areas. It has been found in depths between 24 and 950 m (see Kussakin 1967, 1982). In the Polarstern col­ lections it was present in the area of the Antarctic Peninsula at depths between 86 and 449 m (shallowest station: 20 m, Admirality Bay, King George Island; no station deeper than 449 m), in the Weddell Sea between 198 and 1,145 m (no deeper station). So the species is eurybath; we do not know to which maximal depth it penetrates the bathyal continental ^ slope.

B) Polymorphism Polymorphism was studied in populations from the Ant­ arctic Peninsula to the southern Weddell Sea. A statistical comparison of the animal's size is not very in­ structive, for this purpose the samples are too small. Nevertheless it seems that in some localities distinct dif­ ferences exist: near Signy Island (South Orkneys) adult males measured 50 to 63 mm length, ovigerous females 52 to 62 mm; equivalent sizes from Admirality Bay (King 15^ George Island, South Shetlands) are 60-67 mm and 66 - 73 mm, in the Gould Bay (southern Weddell Sea) 57 - 78 mm and 60 - 78 mm. Comparing the quotient length: width, no clear trend was discernible, variations Fig. 2. Authors mentioning the occurrence of C. trilobitoides: 1 Cals within the samples are too great (examples for the 1977; 2 Cleret 1973; 3 Eights 1833; 4 Hale 1937; 5 Hale 1952; 6 Hodg­ quotient length/width: Signy Island: in males from 0.94 son 1910; 7 Kussakin 1967; 8 Kussakin and Vasina 1982; 9 Lipps et al. 1979; 10 Monod 1926; II Nierstrasz 1931; 12 Richardson 1913; to 0.98, in ovigerous females from 1.04 to 1.11; 13 Sheppard 1933; 14 Sheppard 1957; 75 Studer 1879; 75 present paper Admirality Bay: in males 1.09-1.12, in ovigerous 129 females 1.04-1.10; Gould Bay: in males 1.08-1.18, in The features of the pleotelson show similar regional ovigerous females 1.16-1.38). Generally animals are trends: at the more northern sites the mediodorsal keel slightly longer than wide, some specimens from Signy bears only few and large spines, especially around Signy Island are sUghtly wider than long. Island; the pleotelsonic apex has clearly a longer point Those features used by Sheppard (1933) and than in specimens from the southwestern and southern Carvacho (1977) to describe the differences between C. Weddell Sea (in Table 1: quotient (length of pleotelson cornuta and C. trilobitoides show an important variabili­ minus caudal point)/(length of caudal point). In the ty. The pleotelsonic mediodorsal spines and the structure southern localities the number of lateral and mediodorsal of the two dorsal lobes of the cephalothorax, which spines increases, the spines are smaller. adorn the area between the eyes, have within a single The animals from the Bransfield Strait (Fig. 3) bear a population a relatively uniform appearance. Figures 3 to singular feature: a pair of dorsal spines is present on both 9 show for each locality these details from a selected sides of the pleotelsonic keel. In no other locality could adult male and a mature female. this structure be found. A striking feature is the sexual dimorphism of the The diagonal ridges on the anterior pleotelson show cephalothoracic lobes in the population from Admirality an increased number of small tubercles in specimens Bay (King George Island), where the male specimens from the southern Weddell Sea. have a relatively smooth caudal surface of these lobes, Some features of the figured specimens are summa­ while some deep notches are present in females. This di­ rized in Table 1. morphism was also noted, though less pronounced, in In general terms, the populations from the more specimens from Signy Island. While in the populations northern localities have similar features, some of these from the western shelf of the Weddell Sea the lobes of are accentuated in the animals from Signy Island (num­ both sexes are relatively smooth, the lobes of specimens ber of spines); the other extreme to the latter morphotype from Filchner depression, Gould Bay and Bransfield is found in the Filchner-depression, with related morpho- Strait (north of Joinville Island) have deep posterior types east and west of it. The population from Vestkapp notches. has an intermediate position. But not only both extremes

Fig. 3. Features of C. trilobitoides. Left side: male (M), right side: oovigerous female (F). Above: ceph­ alothorax in dorsal view; center: pleotelson in lateral view; below: pleotelson and first 3 pleonites in dor­ sal view. Locality: Bransfield Strait 130

Fig. 4. Features of C. trilobitoides (arrangement as in Fig. 3). Locality: Admirality Bay, King George Island

have very characteristic peculiarities, as already men­ The propodus bears 2 rows of composite spines, one tioned for the pair of telsonic spines in the population of which is longer (hatched in Fig. 10); distally between from Bransfield Strait. both rows a single spine is present (marked with "x" in Searching for further features the subchelate male Fig. 10). Groups of similar morphotypes cannot be pereopod 2 has been compared. Figure 10 shows, in addi­ defined, but there are clear differences between C. tion to material from the localities already discussed, the pastemaki (Fig. 10 A) and C. trilobitoides. C. pastemaki perepod 2 of a male from Zadovski Island (South Sand­ has considerably fewer spines, the distal concavity of the wich Islands) (Fig. 10: B), and for comparison the sub- propodal palm is longer, the medial spine between the two chela of C. pastemaki, the second, considerably smaller rows is lacking. This comparison is important to gain an { species of the genus Ceratoserolis. idea of the variations that occur at the species level.

Table 1. Comparison of morphological features of C. trilobitoides from different localities

Locality Bransfield Admirality Signy Vestkapp N.E. of Filchner- Gould Strait Bay Island Halley depression Bay

Cephalothoracic lobes notched sex. di­ sex. di­ relatively notched notched notched morphic, morphic, smooth smooth smooth Chephalothoracic lobes notched sex. di­ sex. di­ relatively notched notched notched morphic, morphic, smooth smooth smooth No. of mediodorsal 7-8 7 4-7 8-10 9-12 10-11 10-14 spines of pleotelson No. of lateral spines of 13-17 12-18 10-11 11-16 17-20 19-27 18-21 pleotelson Quotient 9.3 7.5 5.3 9.7 15.3 32.8 16.4 (length of pleotelson)/ (length of terminal spine) 131

Fig. 5. Features of C. trilobitoides (arrangement as in Fig. 3). Locality: off Signy Island

Fig. 6. Features of C. trilobitoides (arrangement as in Fig. 3). Locality: Vestkapp, eastern Weddell Sea 132

Fig. 7. Features of C. trilobitoides (arrangement as in Fig. 3). Locality: NE of Halley Bay

Fig. 8. Features of C. trilobitoides (arrangement as in Fig. 3). Locality: Filchner-depression 133

Fig. 9. Features of C. trilobitoides (arrangement as in Fig. 3). Locality: Gould Bay

C) Pigment Patterns physiological adaptations. Though the Southern Polar Ocean is relatively homogeneous in comparison with Figure 11 shows some typical dorsal pigment patterns other oceans we must assume, that for the stenoecic ant­ from the area studied. The colour is produced by a grey- arctic invertebrates, which live at the lower limit of the yellow tinge of the integument, in transparent specimens the inner organs shine through, many small, dark grey or temperature range near the freezing point, already small brown chromatophores determine the general colour, ac­ variations of the environmental conditions will have im­ cumulations of larger brown chromatophores are re­ portant effects. While the upper sublittoral water of sponsible for the patches. Though the arrangement of Admirality Bay has temperatures of near -2.0°C to the brown patches varies individually within the popula­ + 2.5°C (measured 1977/1978: Presler 1980), we find in tions, e.g. individuals from Admirality Bay (Fig. 11:1) the Filchner-depression on the bottom a supercooled may have smaller patches than in the figured specimen, it water (-2.2°C -2.3°C: Gammelsr0d and Slotsvik is possible to define a basic pattern for each population. 1981) of high salinity (probably throughout the year). Several small patches, often occurring in single central Possibly physiological differences can be measured when rows on the coxal plates, together with a light integument populations of both areas are compared. An indication are typical for most animals from the northern localities. for differences in the tolerance for small variations of Specimens from Bransfield Strait have a sUghtly darker temperature and salinity is the mortality we observed integument. A pair of anterolateral and a terminal brown while keeping specimens in acquaria. Though it was in­ patch are present on the pleotelson of specimens from tended to keep temperature constantly at -1 °C and Admirality Bay, Vestkapp and Gould Bay. No brown salinity at 33.3%o, due to technical problems some varia­ patches can be seen in the population from Filchner-de- tions occurred (temperature up to + 3 °C, salinity around pression, where the general colour is a bluish dark grey. 34.5%o). These changes are stress-factors and probably In the Gould Bay very dark as well as lighter specimens caused several animals to die (physiological mechanisms occur together with intermediate forms. are not known). Specimens from Filchner-depression lived only for 2-3 weeks. Figure 12 shows that the specimens from Signy Island survived cultivation best while those from Gould Bay seem to be very delicate. But D) Physiological Races as we do not know what effect the change in pressure It is probable that the genetic variability described will during capture has, we must be careful with the interpre­ not be restricted to the phenotypes but will also show in tation of Fig. 12. 134

Fig. 10. Subchela of male pereopod 2. A: Cpas- ternaki, specimen of 31 mm length, from 72°31.64'S 17°34.97'W. 5-G; C. trilobitoides. B: Specimen of 49 mm length, from SE of Za- dovski Island (South Sandwiches), "Discovery" Station 363 (B.M.N.H.). C: Specimen of 63 mm from Bransfield Strait. D: Specimen of 53 mm from off Signy Island. E: Specimen of 64 mm from Vestkapp. F: Specimen of 79 mm from NE of Halley Bay. G: Specimen of 62 mm from Gould Bay. Longer spine row of propodus hatched, medial composite spine of propodal palm marked with "x"

E) Systematics: Synonymy with C. comuta (Studer, 1879) 2) "... that (= the terminal segment) of S. cornuta is longer than broad with a much more acute posterior ex­ A comparison of the type material of C. cornuta and tremity and with a longer terminal spine...". Figures specimens designated by Sheppard as C. comuta and C. 3-9 show the variability of this feature, no exact trilobitoides with the present collection was necessary to boundary can be drawn between morphotypes. The same clarify the confusion about these two species. Among the is true for the remaining features: 3) mediodorsal spines material of the present study the variety from Signy Is­ of pleotelson, 4) length of coxal plates of the seventh land is a typical "cornuta"-ioxm, which is distributed in thoracic somite, 5) the colour. several more northern antarctic places (Crozet Islands, Carvacho (1977) emphasized another feature: "... South Orkneys, South Sandwich Islands: Sheppard chez S. cornuta elle ( = 1'ornamentation situee derriere 1933). Sheppard (1933) discusses the following features: chaque oeil) prend la forme d'un cone; tandis que chez S. 1) "... The shape of S. comuta,..., is almost circular, trilobitoides il s'agit d'une structure trilobulee...". This whilst that of S. trilobitoides is broadly ovate...". It has feature is dimorphic in some populations; smooth lobes already been mentioned that the quotient length/width also appear in other populations, which have a morpho­ varies within populations and no striking differences logy of Sheppard's trilobitoides. could be found when comparing specimens from differ­ We must conclude that C. cornuta (Studer 1879) is a ent localities. junior synonym of C. trilobitoides (Eights 1833) and that 135

Fig. 11. Variation of colour pattern in popula­ tions of C. trilobitoides (drawn after photo­ graphs of living specimens). The map shows the Weddell Sea with important currents (ar­ rows; F: area of Filchner-depression). The depth of the localities is indicated. Localities: 1 King George Island, 2 Elephant Island, 3 off Joinville Island (62°39'S 55°45'W), 4 Coro­ nation Island, 5 Vestkapp(72°25'S 16°27'W), 6 eastern side of Filchner-depression, 7 Filch­ ner-depression, 8 Gould Bay (72°18'S 41°26'W); the population from Gould Bay consisted of darker and less dark specimens the "cornuta" morphotype is only one of several local the distribution of pigment patterns and the many inter­ varieties of a widely distributed species. This synonymy mediate features that connect different morphotypes. To was first suggested by Hodgson (1910), with our richer separate two morphospecies would be a subjective act material it can be confirmed. and yield artificial taxa. The 'colour-species' proposed by Cals (1977: C Discussion maculatovirgata, C. albohirsuta, C. griseostrigosa, C. The question whether phenotypical differences indicate lineatocostata), superficially described and without the presence of several species or not cannot always be designated type material, have not to be discussed seri­ solved. The crucial point is if a reproductive isolation is ously in the Ught of the present results. probable or not. As soon as indications for gene flow are Intraspecific variability of serolids was discussed by found, we must suppose that we are dealing with a single Holdich and Harrison (1980). The Austrahan species biospecies (see Willmann 1985). Then C. trilobitoides Serolis minuta shows differences which do not justify the should be considered as a widely distributed, very separation of species. S. minuta also has an area of dis­ variable biospecies, which because of a reduced panmixis tribution which includes important climatic differences is in the process of speciation, which resulted until now (from about 26° S to 37°S). To decide whether a varia­ in races that still can exchange genes. This is suggested by tion is a new species or not Holdich & Harrison recom- exact studies on this subject are lacking. It is difficult to explain why the populations living in the aphotic zone on the bottom of the deep Filchner depression have such a dark coloration.This adaptation might have occurred in the shallower Gould Bay. Cryptic coloration and active (physiological) colour change of serolids have been de­ scribed by Moreira (1974). Physiological changes of pig­ mentation have not been observed in C. trilobitoides, though many specimens were kept for several months on different sediments in aquaria. The patterns are fixed by the arrangement, size and colour of chromatophores. Another aspect of the present findings is important for discussions on antarctic ecology: This species shows through its local races how immobile it is and how few JAN APR 1985 possibilities for the colonization of unpopulated areas Fig. 12. Survival of C. trilobitoides kept in acquaria at about - 1 °C these animals have. The existence of these races is pos­ and a salinity of 33.3%o. The specimens were collected at the following sibly an indication for the low tolerance of disturbances localities: 1 Gould Bay (depth 660 m), 2 Signy Island (depth 86 m), 3 Vestkapp (230 m), 4 Admirality Bay, King George Island (450 m), of some benthic invertebrates. It is not known how many 5 NE of Halley Bay (200 m) offspring this species can produce per unit of time (the specimens possibly live 6 years, a female can produce about 100 eggs: Luxmoore 1982; embryonal develop­ mend to compare a large number of specimens from ment lasts about 2 years: Wagele, in press), but it seems different samples. very probable that productivity is as low as in other polar Considering the variability of these isopods we must invertebrates (see Clarke 1982). This phenomenon, com­ ask if the genus Ceratoserolis really can be separated bined with immobiUty and the lack of swimming stages from Serolis, as proposed by Cals (1977) for the species results in genetically stable populations which have only 5. trilobitoides, S. cornuta and S. pasternaki (without few contacts with their closest neighbours. This is most naming a type species, which should be S. trilobitoides, conspicuous in the southern Weddell Sea, where between as this species was principally discussed by Cals). 77°39.63'S 35°23.91'W and 77°42.25'S 36°48.09'W a It is obvious that "Serolis" in its present state is a sharp separation of pigment patterns has been found polyphyletic genus containing species of varying mor­ (Fig. 11:6 and 7). In this area hydrographical conditions phology, as those oval animals without protruding coxal might form a barrier for migrations. As already men­ plates (e.g. S. ovata, S. latifrons, S. elliptica) or the tioned the Filchner-depression has at its bottom one of species with long coxal plates and mediodorsal spines on the coldest water bodies, which flows from under the cephalothorax and tergites (e.g. S. johnstoni, S. ger- Shelf Ice to the north and is partly led back south, where lachei, S. spinosa) or species with a shortened thorax it disappears again under the Filchner Ice Shelf (Car- (e.g. S. tropica, S. carinata, S. mgrayi). To define genera mack and Foster 1975). The Filchner population possibly from monophyletic groups of species is very useful, espe­ has special adaptations to very low temperatures; it cially in course of a revision, which for serolids is still seems to have contacts to the more western population of lacking. Therefore the author feels that the genus the Gould Bay, where dark pigmentation is also fre­ Ceratoserolis should not be rejected. Ceratoserolis can quent. be recognized by its nearly circular shape, the protrud­ ing, caudally directed coxal plates, the long epimera of Acknowledgements. This study was supported by the grant DFG-Wa- pleonites 2 and 3, which nearly reach or surpass the apex 530/1. The Alfred Wegener Institut (Bremerhaven, FRG) provided of the last coxal plate, the sculptured cuticle between the logistic and technical support. The author is especially grateful for the eyes, the visible suture lines of coxal plates 2 to 4, the loan of a temperature-controlled container, which made several aspects of the present study possible. The author's wife, Heike Wagele, kindly typical pleotelson, the absence of dorsal spines on took care of the aquaria during the voyage Cape Town - Bremerhaven. cephalothorax or tergites. The similarities between C. pasternaki and C, trilobitoides have been noted by Kus- sakin (1967) as well as the differences, of which the size of the sexually mature animals and the form of the male References P2 are the most conspicuous. These differences are not within the range of the polymorphism of C. trilobitoides, Cals P (1976) Polychromatisme, polytypisme scutellaire et modalites de C. pasternaki really is a separated species, no hybrids la speciation chez des Crustac6s marins subantarctiques. SeroHdae have been found until now. (Isopodes fabelUferes). Bull Soc Zool France 101:1027-1028 Cals P (1977) Derive continental et speciation du complex Ceratose­ The different pigment patterns of C. trilobitoides rolis nov. gen., Crustaces antarctiques benthiques connus de I'Arc de possibly are an adaptation to the colour of the sediment. la Scotia aux iles Kerguelen. C R Acad Sci, Ser D 284:2273-2276 137

Carmack EC, Foster TD (1975) Circulation and distribution of oceano- Lipps JH, Roman TE, DeLaca TE (1979) Life below the Ross ice shelf, graphic properties near the Filchner Ice Shelf. Deep-Sea Res Antarctica. Science 203:447-449 22:77-90 Luxmoore RA (1982) Moulting and growth in serolid isopods. J Exp Carvacho A (1977) Sur une importante collection d'isopodes des lies Mar Biol Ecol 56:63 - 85 Kerguelen. CNFRA 42:173 -191 Monod T (1926) Tanaidaces, isopodes et amphipodes. Resultats du Clarke A (1982) Temperature and embryonic development in polar voyage de la Belgica en 1897-1899. Exp Antarct Beige Rapp Sci marine invertebrates. Int J Invert Reprod 5:71 -82 Zool 4:1-67 Cleret JC (1973) Invertebres de I'infralittoral rocheux dans I'archipel de Moreira PS (1974) Cryptic protective coloration in Serolis laevis and Kerguelen. 2. Isopodes et Tanaidaces. CNFRA 32:31 -36 Serolis polaris (Isopoda, Flabellifera). Crustaceana 27:1 -4 Eights J (1833) Description of a new Crustaceous animal found on the Nierstrasz NF (1931) Die Isopoden der Siboga-Expedition. 3. Isopoda shores of the South Shetland Islands. Trans Albany Inst 2:53-57 genuina. 2. FlabeUifera. Siboga Exp 32:123-233 Gammelsr0d T, Slotsvik N (1981) Hydrographic and current measure­ Nordenstam A (1933) Marine Isopoda of the families , Ido- ments in the Southern Weddell Sea 1979/80. Polarforschung theidae, Pseudidotheidae, Arcturidae, Parasellidae, Stenetriidae, 51:101-111 mainly from the South Atlantic. Further Zool Res Swed Antarct Exp Hale HM (1937) Isopoda and Tanaidacea. Australas Ant Exp Sci Rep. 1901-1903 3:1-284 SerC2:l-45 Presler P (1980) Phenological and physiological observations carried Hale HM (1952) Isopoda, famiHes Cymothoidae and Serolidae. BAN- out during the first wintering at the Arctowski Station in 1977. Pol ZARE 1929-1931, Rep Ser B 6:21 - 36 Arch Hydrobiol 27:245-252 Hodgson TV (1910) Isopoda. Nat Antarct Exp 1901 -1904, 5:1-77 Richardson HE (1913) Crustaces Isopodes. Deuxieme Expedition Ant- Holdich DM, Harrison K (1980) Morphological variation in the Serolis arctique Franfaise (J Charcot) 1908-1910, Paris, pp 1 -24 minuta group (Isopoda: Serolidae) from AustraHan waters. Zool J Sheppard EM (1933) Isopod Crustacea Pt. 1. The family SeroUdae. Linn Soc 68:373-386 Discovery Rep 7:253 - 362 Kussakin OG (1967) Isopoda and Tanaidacea from the coastal zones of Sheppard EM (1957) Isopod Crustacea Pt. 2. The suborder Valvifera: the Antarctic and Subantarctic. In: Biological results of the Soviet families: Idotheidae, Pseudidotheidae and Xenarcturidae fam. n. Antarctic expedition (1955-58), 3. Issled Fauny Morei 4:220-380 With a supplement to the Isopod Crustacea, Pt. 1. The family Kussakin OG (1982) Dopolnenie k faune ravnonogih rakoobraznyh Serolidae. Discovery Rep 21:141 -198 sel'fovyh zon antarktiki (po materialam sovietskoj antarkticeskoj Studer T (1879) Beitrage zur Kenntnis niederer Thiere von Kerguelens- ekspedicii 1965-1968 gg.). In: Kafanov AI, Kussakin OG (eds) land. Arch Naturgesch 45:19-34 Fauna i raspredelenie rakoobraznyh notal'nyh i antarkiceshik vod. Wagele JW (in press) On the reproductive biology of Ceratoserolis Vladivostok: 73-105 trilobitoides (Crustacea: Isopoda): latit-udinal variation of fecundity Kussakin OG, Vasina GS (1982) Addition to the fauna of benthic Iso­ and embryonic development. Polar Biol poda and Gnathiidea (Crustacea) of subantarctic waters of the Willmann R (1985) Die Art in Raum und Zeit. Parey, Berlin Hamburg, Indian Ocean. 1. Isopoda (Flabellifera and Anthuridea). Tethys 207 pp 10:261-273